Submersible pumping systems are often deployed in wells to recover petroleum fluids from subterranean reservoirs. Typically, a submersible pumping system includes a number of components, including an electric motor coupled to one or more high performance pump assemblies. Production tubing is connected to the pump assemblies to deliver the petroleum fluids from the subterranean reservoir to a storage facility on the surface.
The motor is typically an oil-filled, high capacity electric motor that can vary in length from a few feet to nearly one hundred feet, and may be rated up to hundreds of horsepower. Prior art motors often include a fixed stator assembly that surrounds a rotor assembly. The rotor assembly rotates within the stator assembly in response to the sequential application of electric current through different portions of the stator assembly. The motor transfers power to the pump assembly through a common shaft keyed to the rotor. For certain applications, intermediate gearboxes can be used to increase the torque provided by the motor to the pump assembly.
Power is typically provided to the motor from a variable frequency drive (or variable speed drive) through an output (step up) transformer. The variable frequency drive is provided power from a local electrical power grid. The electric submersible pumping system typically includes a long power cable that extends from the surface facilities to the electrical motor positioned downhole.
Petroleum reserves are often located in isolated, rural locations. In certain areas, access to an established power grid is impossible or cost-prohibitive. There is, therefore, a need for a system that can reliably and efficiently provide electrical power to electric submersible pumps without access to an established power grid. It is to this and other deficiencies in the prior art that the present invention is directed.